Identifying human parieto‐insular vestibular cortex using fMRI and cytoarchitectonic mapping

Abstract

The parieto-insular vestibular cortex (PIVC) plays a central role in the cortical vestibular network. Although this region was first defined and subsequently extensively studied in nonhuman primates, there is also ample evidence for a human analogue in the posterior parietal operculum. In this study, we functionally and anatomically characterize the putative human equivalent to macaque area PIVC by combining functional magnetic resonance imaging (fMRI) of the cortical response to galvanic vestibular stimulation (GVS) with probabilistic cytoarchitectonic maps of the human parietal operculum. Our fMRI data revealed a bilateral cortical response to GVS in posterior parieto-insular cortex. Based on the topographic similarity of these activations to primate area PIVC, we suggest that they constitute the functionally defined human equivalent to macaque area PIVC. The locations of these activations were then compared to the probabilistic cytoarchitectonic maps of the parietal operculum (Eickhoff et al. [2005a]: Cereb Cortex, in press; Eickhoff et al. [2005c]: Cereb Cortex, in press), whereby the functionally defined PIVC matched most closely the cytoarchitectonically defined area OP 2. This activation of OP 2 by vestibular stimulation and its cytoarchitectonic features, which are similar to other primary sensory areas, suggest that area OP 2 constitutes the human equivalent of macaque area PIVC.

Body ownership and embodiment: Vestibular and multisensory mechanisms

“…Accordingly, we propose that this spatial dissociation between self and body location (that is very prominent in out-of-body experiences) might reflect partial disembodiment as it can be observed in patients with autoscopic phenomena in whom vestibular illusions are often associated symptoms [14,17,83] and in healthy subjects using multisensory conflict and virtual reality [84]. This observation is supported by the activation of the vestibular cortex by galvanic vestibular stimulations [6,32,37,46,51,85,110] overlapping with key structures of embodiment such as the TPJ and the temporooccipital cortex [5,16].…”

“…Congruently, epileptic patients with vestibular aurae suffer from lesions surrounding the superior temporal gyrus and the temporoparietal cortex [99,107]. This location has also been confirmed by functional neuroimaging studies in healthy subjects using caloric and galvanic stimulation of the peripheral vestibular system revealing unanimously predominant activations centered on the TPJ and insula [6,19,20,32,39,46,47,50,51,70,72,85,94,95,110,112,118] with activations in the superior temporal gyrus, posterior insula, inferior parietal lobule (angular and supramarginal gyri), and postcentral gyrus. Although many regions surrounding the TPJ/insula have been found activated, opinions concerning the exact location of the human homologue of the PIVC differ (Fig.…”

“…In healthy subjects, sense of body ownership and self-attribution of actions are also more specifically related to right posterior insula activity [49,115]. Also, there is an overall right hemispheric dominance for the vestibular cortex [39,46,50,51,112], and the integration of vestibular and proprioceptive cues seems to involve particularly the right TPJ (see Bottini et al [19]). In the case of autoscopic hallucinations, lesion sites are mostly located in right parieto-occipital and temporo-occipital cortex with less involvement of the TPJ [13,15].…”

Visual-vestibular processing in the human Sylvian fissure

“…This information is of critical relevance for guiding locomotion and for process- There is accumulating evidence that the potential hub of the cortical vestibular network is located in a region including the posterior part of the Sylvian fissure (also called lateral sulcus), perisylvian cortex, and the posterior insula. At this site, functional imaging studies in humans found activation during vestibular stimulation (Bense et al 2001;Dieterich et al 2003;Eickhoff et al 2006;Fasold et al 2002;Lobel et al 1998) and labeled it the parieto-insular vestibular cortex (PIVC), following terminology in the primate brain (Akbarian et al 1988;Chen et al 2010;Grüsser et al 1990; Shinder and Newlands 2014).…”

“…This information is of critical relevance for guiding locomotion and for process- There is accumulating evidence that the potential hub of the cortical vestibular network is located in a region including the posterior part of the Sylvian fissure (also called lateral sulcus), perisylvian cortex, and the posterior insula. At this site, functional imaging studies in humans found activation during vestibular stimulation (Bense et al 2001;Dieterich et al 2003;Eickhoff et al 2006;Fasold et al 2002;Lobel et al 1998) and labeled it the parieto-insular vestibular cortex (PIVC), following terminology in the primate brain (Akbarian et al 1988;Chen et al 2010;Grüsser et al 1990; Shinder and Newlands 2014).However, the vestibular network in the posterior Sylvian fissure is likely more complex and might include at least one additional area, named posterior insular cortex (PIC), that responds to vestibular stimuli as well as to visual object motion and potentially serves as a site of multisensory integration .The anatomical and functional relationship between PIC and PIVC is still unclear, because both areas have not yet been investigated in the same participant. Therefore, in this study we aimed to define and compare the regions known as PIVC and PIC directly in the same participants.…”